What exactly is a quad, as it relates to modern technology?

(The Memory Alpha article seems limited.)

• If you just extend Kryder's Law to the 24th century, data storage will be about 2^350 times more dense. So.. erm.. it's a lot. Nov 14, 2011 at 16:31
• Fun fact: 2^350 is about 2.2 quattuortrigintillion, which is about 30 orders of magnitude greater than the current average storage density. Nov 14, 2011 at 22:34
• @ChadLevy: that is interesting, and also renders me entirely at a loss to determine why the characters in Star Trek don’t just say “quattuortrigintillions”. Feb 3, 2015 at 11:52

Two quotes from the link you've provided answer this. First, it is not a consistently used amount:

The terms quads and kiloquads in TNG were used in a manner consistent with the system defined in the Technical Manual. However, by the time Voyager was airing, they started using extremely large numbers that lacked internal consistency, such as "billions of gigaquads" and "billions of teraquads."

Secondly, it is a deliberately vague amount, since:

The terminology "quad" was used to detract from comparisons possible with modern-day computing power, since reality frequently outstrips fiction when it comes to computer science.

If my memory serves me correctly, this second quote was also referenced in the TNG technical guide.

• I can't find it in the Writer's Technical Manual they sent me when I was pitching to them, but if it doesn't contain that 2nd quotation it has something close. I remember they had statements like, "This section contains so many quads and that contains so many more quads..." and ends with a comment that the size of a quad will never be specified. Nov 14, 2011 at 15:44
• @TangoOversway: you may have got me there; perhaps it was the Star Trek Encyclopedia? I don't have them any more so I can't check. Nov 14, 2011 at 19:04
• Sorry, by "I can't find it in..." I meant I was looking for it, but I couldn't find it in the time I had, but I know there was a statement that was close to that somewhere in the guides and material they sent to me in my pitch kit. So you're close, and that's the general idea. It just might be different wording. Nov 14, 2011 at 22:27
• @TangoOversway: OK, thanks for the feedback. Nov 15, 2011 at 6:46
• Given this wise choice of inventing a unit without defining it, I wonder why they nonetheless specified the memory capacity of Wesley’s nanites in Evolution in gigabytes and Data’s memory capacity in The Measure Of A Man in bits... Dec 8, 2011 at 2:02

My understanding of a "quad" is a "quantum digit", equivalent to what is known in real-world computer science as a "qubit".

Like a classical electronic "bit" (binary digit), a qubit has two possible states; on and off. However, unlike a classical bit, a qubit can be both on and off at the same time; technically, it's at some state between them, and the set of all possible states is described by the surface of a unit sphere in 3-dimensional space. This is analogous to quantum theory, with Young's Experiment and the famous "Schrodinger's Cat" analogy. This allows a qubit to store vastly more state information, and also allows for algorithmic processing in which a bit can be considered to be both on and off at the same time, necessary for applications like probability mechanics, large number theory, and cryptography.

As of the writing of all of the TNG-era series (TNG, DS9, Voyager), this branch of comp sci was pretty well-defined if not yet fully realized, and was probably drawn from to conceptualize the computers aboard a starship. As of right now you can count the number of qubits contained in our most advanced quantum computers on the fingers of both hands; by the 24th century, given the exponential pace of technological development, they're dealing with data in the billions (giga), trillions (tera) and even quadrillions (peta) of "quads".

• Great answer! This is what I was getting at: not so much an in-universe explanation, but one involving reality, in this case quantum computing. Nov 14, 2011 at 17:53
• Actually, the answer's off. A quad is nothing like a quantum digit. It's a measurement of an amount of memory. It's more like a kilobyte or terabyte than like a bit or byte. Nov 14, 2011 at 18:10
• And a qubit is an amount of memory; a significant one when you take into account what it can do. A qubit, with the ability to be any value on the surface of a 3-dimensional sphere, means that a single quad can be any complex number (including any real number) between 0 and 1. That means 1 quad can be any integral number (using the factional part, with some system for signing inherent in the value), and 2 quads (for significand and exponent) can be any real number. Compare that to the relatively sharply-limited 64-bit integer and 128-bit decimal. Nov 14, 2011 at 18:51
• Thus, with the ability to represent any number or single value (including non-numeric data; remember that characters are just byte values on a codepage) in one qubit, a single qubit can easily replace several thousand bits of electronic memory, especially for large numbers. Nov 14, 2011 at 18:55
• @KeithS: I'm not arguing about the meanings of other words, I'm just pointing out that in the Writer's Guide, it was made clear that quad was an amount of memory which Sternbach and Okuda refused to specify. Nov 14, 2011 at 22:28

it seems that the terms are incorrect for describing 3d "crystalline" matrix computing. now, IIRC, it was referenced as units called "quads" in which data was manipulated. this unit was a 3d construct of a 4x4x4 "bit" arranged in a 4x4x4 "byte" called a "quad." which would make it a 262144 bit unit.